Knitted fabric expanders of the aforementioned type are already known through DE-PS No. 24 56 466 and DD-PS No. 204 114. Holders/expanders positioned beneath the needle beds for expander guide bars have the advantage that no carriers or adjusting rails for the guide bars are necessary above the needle beds, which would form an additional hinderance for the yarn guide. Hitherto proposed or known designs however, have the disadvantage that the guide bars can only be removed from the holders with difficulty, and adjustment of the holders is, in reality, only possible if a piece of knitting, the borders/edges of which are knitted around the guide bars, has left the guide bars again at the lower end. A further disadvantage exists in the fact that it is necessary to provide a good means of support for the guide bars in their region beneath the comb gap, due to the free exposed end of the guide bars projecting through the comb gap, which is only possible by a greater number of guide rollers or pairs of rollers, making the device expensive in terms of construction.